Astronomy 101
The Solar System
Tuesday, Thursday
Tom Burbine
tomburbine@astro.umass.edu
Course
• Course Website:
– http://blogs.umass.edu/astron101-tburbine/
• Textbook:
– Pathways to Astronomy (2nd Edition) by Stephen Schneider
and Thomas Arny.
• You also will need a calculator.
• There is an Astronomy Help Desk that is open
Monday-Thursday evenings from 7-9 pm in Hasbrouck
205.
• There is an open house at the Observatory every
Thursday when it’s clear. Students should check the
observatory website before going since the times may
change as the semester progresses and the telescope
may be down for repairs at times. The website is
http://www.astro.umass.edu/~orchardhill/index.html.
HW #10, #11, #12, #13, #14, and #15
• Due March 30th at 1 pm
Exam #3
• Next Thursday
• Covers everything from February 23rd to today
• Formulas:
density = mass/volume
volume of sphere = (4/3)r3
n = no(1/2)(t/half-life)
•
F = GMm/r2
• I wouldn’t forget the formulas that we learned
previously
Geologic Time Scale
• A scheme to relate stratigraphy to time
• Divided according to the rock types and type of
fossils found in each one.
Eras
• Paleozoic (the era of "ancient life“) is
characterized by fossils of invertebrates, primitive
tetrapods, etc.
• Mesozoic (era of "middle life“) is characterized
by fossils of dinosaurs, etc.
• Cenozoic (era of "recent life“) is characterized by
mammals and modern plants and invertebrates.
Why is there such a large
age difference between the
beginning and end of the
Cambrian?
Ma – million years
http://geomaps.wr.usgs.gov/socal/geology/geologic_history/images/geologic_time_scale.jpg
• Cambrian is the earliest period where rocks are
found with numerous large multicellular
organisms that could be found as fossils
http://pubs.usgs.gov/gip/geotime/fossils.html
http://creationwiki.org/pool/images/thumb/c/c5/Evolution_timeline.jpg/400px-Evolution_timeline.jpg
http://www.cityastronomy.com/geologic-earth-moon-graphic.bmp
http://www.psrd.hawaii.edu/WebImg/LunarTimeScale.gif
http://www.etsu.edu/physics/etsuobs/starprty/21200mwc/moonmap.jpg
Moon
• http://www.youtube.com/watch?v=hTKedyQQkZQ
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•
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http://apod.nasa.gov/apod/ap010218.html
The Moon's orbital period is 27.322 days
Rotation period and orbital period are the same
This means we keep on seeing the same side of
the Moon
http://home.xtra.co.nz/hosts/Wingmakers/Moon.html
Phases of Moon
http://www.moonphases.info/images/moon-phases-diagram.gif
http://media.skyandtelescope.com/images/Moon-Phases-3x3-lbl.jpg
Moon
• The Moon is the only know natural satellite of Earth.
• Compared with the satellites of other planets of the solar
system, The Moon is a large moon with a diameter of
3476 km and a mass of 7.349 x 1022 kg.
• The Moon is an average distance of 384,400 km from
Earth and completes its revolution of Earth in 27.32 days.
• The Earth's magnetic field strength is about 100
times higher than the highest value measured on
the Moon by the Apollo missions
• The Moon does not have a magnetic field like the
Earth (North and South Poles) due most likely to
having a solid (or only partially molten) core
• Earth’s core is convecting
• A flowing molten iron-nickel
material can produce electrical
current, which, in turn produces
a magnetic field that surrounds
the Earth
http://geomag.usgs.gov/images/faq/Q6.jpg
Earth
• The first manmade object to land on the Moon
was Luna 2 in 1959
• The first photographs of the far side of the Moon
were made by Luna 3 that same year
Who proposed an American mission to
the Moon in 1962?
Houston, Texas
September 12, 1962
• We choose to go to the Moon. We choose to go
to the moon in this decade and do the other
things, not only because they are easy, but
because they are hard, because that goal will
serve to organize and measure the best of our
energies and skills, because that challenge is
one that we are willing to accept, one we are
unwilling to postpone, and one which we intend
to win, and the others, too.
• The first people to land on the Moon came aboard
Apollo 11 in 1969.
• http://www.nasa.gov/multimedia/hd/apollo11.htm
l
Regolith – Lunar soil
No moisture or organic component compared to terrestrial soil
Who was the 1st person to walk on the
Moon
Who was the 1st person to walk on the
Moon
• Neil Armstrong
• Apollo 11
Who was the 2nd person to walk on the
Moon
Who was the 2nd person to walk on the
Moon
• Buzz Aldrin
• Apollo 11
Moon
• 30,000 craters having a diameter of at least 1
kilometers
• Large craters are named after famous deceased
scientists, scholars, artists
Late Heavy Bombardment
• Period of time approximately 4.1-3.8 billion years
ago where a large number of impact craters
formed on the Moon
• Ages of impact melt rocks from the Melt
clustered between 4.1 and 3.8 billion years
• The largest crater on the Moon, and indeed the
largest known crater within the solar system,
forms the South Pole-Aitken basin.
• Roughly 2,500 kilometers in diameter and 13
kilometers deep
Central part of South Pole-Aitken Basin
http://www.nhk.or.jp/kaguya/archive/index_e.html
South Pole of Moon
• Some craters on Moon are permanently shaded
from the Sun
• May contain water ice
http://shaunmoss.id.au/articles/Billabong.php
• The dark and relatively featureless lunar plains are called
maria, Latin for seas, since they were believed by ancient
astronomers to be water-filled seas.
• They are actually vast ancient basaltic lava flows that
filled the basins of large impact craters.
• Maria are found almost exclusively on the Lunar
nearside, with the Lunar farside
having only a few scattered patches.
Far Side of Moon
Other features on Moon
• Rille - long, narrow depressions in the lunar
surface that resemble channels.
• Floor of Gassendi crater
• Leading theories for rille
formation include collapsed lava
tubes and tectonic extension.
http://en.wikipedia.org/wiki/Image:AS16-120-19295.jpg
Other features on Moon
• Scarp – steep slope or cliff
• The Altai Scarp, which is
the rim of the 860 km wide
Nectaris impact basin, is
nearly 500 km long and
3 to 4 km high.
http://www.lpod.org/?m=20060517
Stratigraphy
• Stratigraphy – studies rock layers and layering
• On planetary bodies, we try to determine the
relative ages when things formed
Principle of Superposition
http://earthsci.org/fossils/geotime/time/Super.gif
http://dept.kent.edu/geology/ehlab/fundamentals/cross_cut.gif
Crater Rays
• Historically, they were once regarded as salt
deposits from evaporated water (early 1900s) and
volcanic ash or dust streaks (late 1940s).
• Now rays are recognized as fragmental material
ejected from primary and secondary craters
during impact events
Crater Rays
• In laboratory sand-layer vertical impacts, the ejecta does
come out evenly around the crater.
• But in a real impact, there are a number of complicating
factors.
• There can be variations in the strength (from pre-existing
fractures in the surface, or inhomogeneties in the target
rock) that lead to "jetting" of ejecta and presumably the
rays.
http://en.wikipedia.org/wiki/Image:AS11-42-6285.jpg
Copernicus
93 km wide
Tycho
85 km wide
http://apod.nasa.gov/apod/image/0503/moon8_mandel.jpg
• Only 2.5% of the surface of the far side is covered
by mare, compared to 31.2% on the near side.
• The likely explanation is that the far side crust is
thicker, making it harder for molten material from
the interior to flow to the surface and form the
smooth maria.
Why do we always see the
same side of the Moon?
• Tidal locking of the Moon's rotation to its orbit
(the phenomenon whereby the Moon spins on its
axis in the same timespan as it takes to orbit the
Earth).
• The lighter-colored areas are called the highlands
• Luna 2 - impact on the surface of the Moon (1959) (USSR)
• Luna 3 - first photos of the far side of the Moon (1959)
(USSR)
• Apollo - Six manned landings on the Moon with sample
return 1969-72.
– (The seventh landing, Apollo 18, was canceled for
political reasons)
• Luna 16 - automated sample return from the Moon (1970)
(USSR)
• Clementine - a joint mission of the Ballistic Missile Defense
Organization and NASA (1994)
• Lunar Prospector - the first NASA mission to the Moon in
almost 30 years (1998-1999)
• SMART-1 - The European Space Agency’s (ESA) spacecraft
orbited the Moon and then crashed into the Moon in
(September, 2006)
Recently
• Japanese SELENE mission (also known as Kaguya) orbited the
Moon
• Goal was "to obtain scientific data of the lunar origin and evolution
and to develop the technology for the future lunar exploration"
http://www.selene.jaxa.jp/en/about/image/img_equipment_001_e.jpg
Pythagoras Crater from SMART-1
http://cdn2.libsyn.com/astronomy/moon_show20.gif?nvb=20081110153501&nva=20081111153501&t=0b619a8f8100c5f7820f5
http://www.space.com/imageoftheday/image_of_day_060626.html
Pythagoras Crater from Selene
Diameter 130 km, Depth 5.0 km
http://wms.selene.jaxa.jp/data/en/hdtv/006/hdtv_006_3/hdtv_006_3_l.jpg
• http://space.jaxa.jp/movie/20080411_kaguya_mo
vie01_e.html
• India's national space agency launched Chandrayaan-1,
an unmanned lunar orbiter, on October 22, 2008.
• Estimated cost is $80 million
• The probe revolved around the Moon for ~1 years (no
longer working)
• Its scientific objectives were to prepare a threedimensional atlas of the near and far side of the moon
and to conduct a chemical and mineralogical mapping
of the lunar surface.
Water on Moon
• Originally scientists thought the Moon was almost
completely dry
Water on the Moon
Grey - H2O and OH absorptions
White line - NASA' Cassini spacecraft
Blue line - NASA's Moon Mineralogy Mapper instrument on the Indian Chandrayaan-1 spacecraft
http://www.nasa.gov/images/content/388950main_ROGER_2-516.jpg
http://upload.wikimedia.org/wikipedia/en/8/89/Chandrayaan1_Spacecraft_Discovery_Moon_Water.jpg
Using Radar from
Chandrayaan-1 spacecraft
Water on Moon
• There are craters on the Moon’s South Pole that
are permanently shadowed from the Sun
• Water could also have been brought to the Moon
by impacting comets
• One liter of water in every metric ton of lunar soil
Chandrayaan-1
http://en.wikipedia.org/wiki/Image:Chandrayaan_1.jpg
• A total of 382 kg of rock samples were returned
to the Earth by the Apollo and Luna programs.
• Apollo - 381.69 kg
Apollo 16
• Luna – 300 g
Luna 16
http://en.wikipedia.org/wiki/Image:Apollo_16_LM.jpg
http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1970-072A
Apollo 15 sample
“Genesis Rock”
Very ancient sample
4 billion years old
http://en.wikipedia.org/wiki/Image:Apollo_15_Genesis_Rock.jpg
Lunar Meteorites
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•
•
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~60 are known
only 1 in 1200 meteorites are lunar
Lunar meteorites are expensive
http://www.meteorites.tv/298-buy-a-lunarmeteorite
• By comparison, the price of 24-carat gold is about
$20 per gram and gem-quality diamonds start at
$1000-2000/gram.
http://epsc.wustl.edu/admin/resources/moon_meteorites.html
Mare
Lunar Highlands
http://epsc.wustl.edu/admin/resources/moon/howdoweknow.html
http://en.wikipedia.org/wiki/Image:Lunar_Ferroan_Anorthosite_60025.jpg
• Highlands – contain Al-rich material
– Plagioclase feldspar – Anorthite - CaAl2Si2O8
• Mare – contain Fe-rich material – basaltic eruptions
– Olivine - (Mg, Fe)2SiO4
– Pyroxene – (Mg,Fe)SiO3
– Ilmenite - FeTiO3
Fe-rich
Al-rich
http://epsc.wustl.edu/admin/resources/moon_meteorites.html
Magma Ocean
Ages
• They range in age from about 3.16 billion years
old for the basaltic samples derived from the lunar
maria, up to about 4.5 billion years old for rocks
derived from the highlands.
How do you form the Moon?
Definitions
• Volatile – evaporates easily
• Refractory – does not evaporate easily
Need to account for these things
• The Moon's low density (3.3 g/cc) shows that it does not
have a substantial iron core like the Earth does.
• Moon rocks contain few volatile substances (e.g. water),
which implies extra baking of the lunar surface relative to
that of Earth.
• The relative abundance of oxygen isotopes on Earth and
on the Moon are identical, which suggests that the Earth
and Moon formed at the same distance from the Sun.
Oxygen Isotopes
• There are three stable isotopes of oxygen
• They have masses of 16, 17, and 18 atomic mass units
%
• 16O
~99.762
• 17O
~0.038
• 18O
~0.200
• The oxygen isotopic ratios (17O/16O and 18O/16O of
silicate rocks from the Earth and Moon are the same
and are different from most meteorites and Mars
http://www4.nau.edu/meteorite/Meteorite/Images/MeteoriteOxygen9.jpg
Giant Impact Hypothesis
• Formation of the Moon as a result of a collision between
the young Earth and a Mars-sized body
• Evidence
– oxygen isotope ratios of Moon identical to those of Earth.
– A large portion of the Moon appears to have been once
molten, and a giant impact scenario could easily have
supplied the energy needed to form such a magma ocean.
– The Earth has a large iron core, but the moon does not. This
may be because Earth's iron had already drained into the core
by the time the giant impact happened. Therefore, the debris
blown out of both Earth and the impactor came from their
iron-depleted, rocky mantles.
Atmosphere
• Not much of an atmosphere since the Moon’s gravity is
so small
• http://www.hulu.com/watch/5117/nbc-news-timecapsule-apollo-11-the-first-moon-landing
Any Questions?